1. Field of the Invention
This invention pertains to alignment tools, and more particularly to alignment tools which use a lead screw driven by a perpendicular input shaft through 45.degree. bevel gears to power a fork which aligns a first body relative to a second body.
2. Description of the Prior Art
Alignment tools for performing relative alignment between two bodies have included supporting structure which rigidly attaches to the first body and has opposed threaded members which are manually adjusted and which bear against the second body. Two opposed bolts, which bear against the second body and which may be manually advanced and retracted through threaded engagement with supporting structure, move the body to which the structure is attached relative to the body against which the bolt ends bear.
One use for such alignment tools is in adjusting the position of a military fighter type aircraft headup display unit mount relative to an aircraft boresight reference line. The unit mount is a frame which accurately cradles the head-up display, so that the display may be removed for maintenance and replaced without losing its precise orientation relative to an aircraft boresight reference line. The unit mount is adjustable in three axes, pitch, roll, and yaw. Commonly, pins which are rigidly attached to aircraft structure, extend through enlarged holes in the unit mount. The supporting structure and bolts attach to the mount at each enlarged hole and bear against each pin. Three or more adjusting devices may be used simultaneously to align the mount.
This method of unit mount adjustment is unsatisfactory because the mechanic must use an end wrench or similar tool to adjust each bolt, and as one bolt is advanced, the opposing bolt must be retracted, necessitating removing the wrench from one bolt head and transferring it to the other.
Also, the head-up display occupies the forward portion of the aircraft cockpit where working space is extremely limited. This means that the adjusting wrench must be swung in an arc about an axis which is approximately transverse to the aircraft longitudinal axis. The wrench can therefore only have a limited length, and may be rotated no more than 90.degree. to 180.degree. before it must be removed and reengaged with the next flat on the bolt head to avoid interference with cockpit structure. These limitations make the boresighting procedure of the head-up display unit mount a difficult and time consuming procedure.